Question

A train moving with a uniform speed covers a distance of $120\,m$ in $2\,s$. Calculate the speed of the train.
A. $60\,m/s$
B. $240\,m/s$
C. $30\,m/s$
D. none of the above.

Answer 1

Hint- The speed can be calculated by dividing the distance travelled with the time taken. Since both distance and time are given, we can directly find the answer by substituting both these values in the equation for speed.

Complete step by step answer:
It is given that a train is moving with a uniform speed.
It means that the train covers equal distance in equal intervals of time.
Let the distance covered be denoted as $d$ .
The value of distance covered by the train is given as
$d = 120\,m$
The time taken t is given as
$t = 2\,s$
We need to calculate the value of the speed of the train.
we know that the speed is calculated as the ratio of distance covered by the time taken.
In equation form we can write it as
$S = \dfrac{d}{t}$
Where, d is the distance and t is the time taken
Distance is defined as the length of the path travelled. It is a scalar quantity. That is, it has only magnitude.
So, the speed is also a scalar quantity.
Now let us substitute the given values in this equation for speed
$S = \dfrac{{120\,m}}{{2\,s\,}}$
$\therefore S = 60\,m/s$
This is the speed of the train.

So, the correct answer is option A.

Note: Speed is the ratio of distance to time taken. Since distance is a scalar quantity, speed is also a scalar quantity. In cases where displacement is given, the ratio of displacement to time will give us the velocity which is a vector quantity. That is, velocity has both magnitude and direction.
Also remember that in cases where the speed is nonuniform we should calculate the average speed which is the ratio of total distance by total time taken.